Plunger operated snap-action electrical switch



Nov. 30, 1965 M. v. scozzAFAvA 3,221,130

PLUNGER OPERATED SNAP-ACTION ELECTRICAL SWITCH Filed Sept. 5, 1963 m16 PIE.. l 42 V/l/l//ll INVEN TOR. M/Z 70A/ 1./ JZWZZF VA BYHM United States Patent O 3,221,130 PLUNGER OPERATED SNAP-ACTION ELECTRICAL SWITCH Milton V. Scozzafava, Arcadia, Calif., assigner to Clary Corporation, San Gabriel, Calif., a corporation of California Filed Sept. 3, 1963, Ser. No. 306,012 Claims. (Cl. 20G- 153) This invention relates to electrical switches and has particular reference to switches operable by depressible keys or plungers.

Data processing equipment such as electronic computers and the like often incorporate keyboards of depressible keys to complete circuits to diiferent units of the equipment so as to perform appropriate functions. The spacing between such keys is generally quite small in order to conveniently group the keys for depression by the operator. This requires that the switches controlled by such keys be correspondingly small and yet generally capable of handling relatively large voltages.

Further, since keyboards of the above type may incor' porate a large number of key controlled switches, such switches must be relatively inexpensive, easy to assemble, etc.

It, therefore, becomes a principal object of the present invention to provide a relatively small and compact key or plunger-controlled switch which eifects disengagement of its contacts with a snap action to quench any arc developed during such disengagement.

i Another object is to provide a key or plunger controlled switch which is economical to manufacture and easy to assemble.

Another object is to provide a key or plunger-controlled switch of the above type which is substantially protected from entrance of dust, dirt, oil and other elements which could cause failure of the switch.

i The manner in which the above and other objects of the invention are accomplished will be readily understood on reference to the following specification when read in conjunction with the accompanying drawing, wherein:

FIG. 1 is a sectional elevation view through a switch embodying a preferred form of the present invention.

FIG. 2 is a sectional view through the switch showing the same in its normally open condition and is taken along the line 2-2 of FIG. 1.

FIG. 3 is a longitudinal sectional view through the switch and is taken along the line 3 3 of FIG. l.

FIG. 4 is an enlarged fragmentary view illustrating the movement of the switch actuating means.

FIG. 5 is a view similar to FIG. 2 but showing the switch in its closed condition.

FIG. 6 is a view, with parts broken away, taken along line 6-6 of FIG. 2.

The switch is comprised of a main body 11 formed of a non-conductive material such as plastic, which is suitably attached to a keyboard top plate 12 adjacent a respective plunger or key stem 13. The stem issuitably guided for reciprocation in aligned guide slots formed in the top plate 12 and in a bottom plate 14 of a keyboard frame.

A pair of electrical contacts 15 and 16 are mounted on the adjacent ends of a pair of elongated leaf springs 17 and 18, respectively. The leaf springs are supported ad jacent their opposite ends in grooves formed between spaced web sections 19 and 21 formed integrally in the body cavity and web sections 33 and 34, respectively, depending from a cap 30. That is, the springs fit between vertical walls 24 and 25 in each of the web sections 1 9 and 21 and vertical walls 26 and 27 in each of the web sections 33 and 34.

3,221,130 Patented Nov. 30, 1965 When the cap is positioned on the body as shown in FIG. 1 the web sections 33 and 34 clamp the springs 17 and 18 in place.

The springs 17 and 18 each have a notch 36 which receives the web 19 to thereby prevent longitudinal sliding of the springs.

The body 11 has an elongated flanged opening 38 which is positioned opposite the stem 13 and is elongated in the direction of stem reciprocaiton for reciving a ball-like roller element 37 formed of a non-conductive material such as plastic.. The cap 30 forms the upper edge of the opening 38.

The ball 37 is free to roll between the stem and the spring 17 and is normally at rest at the bottom of the opening 38 as shown in FIG. 1 when the key stem is in raised position.

A circular camming element 39 is mounted on the stem for cooperation with the ball 37. When the key stem is in its raised position, the camming element 39 will be located above the ball 37 so that the springs 17 and 18 l will be allowed to assume their positions shown in FIGS.

1 and 2 wherein the contacts 15 and 16 are out of engagement with each other.

The key stern 13, carrying a key top 60 at its upper end, is normally held in its illustrated raised position by a tension spring 61 extending along the keyboard plate 14 and under the key stem. Upon depression of the key stem suitable latch means (not shown) becomes effective to latch the stem in depressed position.

Upon depression of the key stem 13, the edge 41 of the camming element 39 will cam the ball 37 to the right in FIGS. 1 and 4, against spring 17, thus swinging contact 15 into engagement with contact 16 an amount sufcient to arch both spring 17 and 18 (see FIG. 5) thereby achieving a wiping action between the two contacts. When the key stem is fully depressed, the at surface 42 will engage the ball 37, as indicated by the dotted lines in FIG. 4 and the full lines in FIG. 5.

- When the key stem is permitted to rise from depressed position, the ball will roll upwardly between the surface 42 of camming element 39 and the surface of spring 17 until it strikes the under surface of the cap 30 as shown in FIG. 4. Continued raising of the stem toward its upper position shown in FIG. 1 will bring a corner 43 formed by the intersection of surfaces 41 and 42 of the camming element 39 a sufficient distance above the horizontal centerline 44 of the ball so that the pressure of the springs 17 and 18 will snap the ball downwardly and outwardly as shown at 45 and 46, allowing the springs to abruptly snap back to their normal positions to quickly quench any `arc developed during disengagement of the contacts.

The main portion of the body 11 is supported above the top plate 12 by depending legs 65 integral with such main body portion to permit electrical leads, ie., 51 and 52, to pass therebetween. Also, holes 47 and 48 are formed in the bottom wall 66 of the body to allow such electrical leads to pass through the wall and to be attached to the respective springs 17 and 18.

The body is located in position on the plate 12 by two depending tenons 63 which tit in suitable locating holes in the plate. Also, the cap and body are secured in place by a screw 64 which passes through both and is screw threaded into the top plate.

Although the invention has been described in detail and certain specific terms and languages have been used, it is to be understood that the present disclosure is illustrative rather than restrictive and that changes and modifications may be made without departing from the spirit or scope of the invention as set forth in the claims appended hereto.

Having thus described the invention, what is described to be secured by United States Letters Patent is:

I.. An electrical switch comprising a pair of electric contact members, at least one of said members including a spring normally maintaining said contact members out of engagement with the other, a plunger having a camming projection thereon, and a roller element in rolling engagement between said plunger and said one of said contact members, said projection being effective upon movement of said plunger in one direction to cam said roller element at right angles to said one direction toward said one contact member whereby to cause engagement of said Contact members, and means other than said plunger for permitting limited movement of said roller element in the direction of movement of said plunger, said projection being effective upon movement of said plunger in the direction opposite said one direction to cam said roller element in said one direction whereby to enable said spring to disengage said contact members.

2. An electrical switch comprising a pair of electric contact members, at least one of said members including a spring normally maintaining said one contact member out of engagement with the other, a plunger having a camming projection thereon, said plunger being movable in opposite directions, a roller element in rolling engagement between said plunger and said one contact member, means other than said plunger for limiting rolling movement of said roller element in either of said opposite directions, said projection being effective upon movement of said plunger in one of said directions and limiting of said roller element by said limiting means to cam said roller element against said one contact member whereby to cause engagement of said contact members, and said projection being effective upon movement of said plunger in the opposite direction and limiting of said roller element by said limiting means to cam said roller element in said one direction whereby to enable said spring member to disengage said contact members.

3. An electrical switch comprising a pair of electric contacts, a leaf spring urging one of said contacts out of engagement with the other, a plunger having a camming projection thereon, and a roller element in rolling engagement between said plunger and said leaf spring, said projection being effective upon movement of said plunger in a first direction to cam said roller element at right angles to said first direction against said leaf spring whereby to cause engagement of said contact members, and means other than said plunger for permitting limited movement of said roller element in the direction of movement of said plunger, said projection being effective upon movement of said plunger in the direction opposite said first direction to cam said roller element in said first direction whereby to enable said leaf spring to disengage said contact members.

4. An electrical switch comprising a pair of electric contact members, a leaf spring urging one of said contact members out of engagement with the other, a plunger having a camming projection thereon, a roller element in rolling engagement between said plunger and said leaf spring, and means other than said plunger for limiting movement of said roller element in the direction of movement of said plunger, said camming projection being effective upon movement of said plunger in a first direction and upon limiting of said roller element by said limiting means to cam said roller to engage said contact members, and said camming projection being effective upon movement of said plunger in the opposite direction and upon limiting of said roller element by said limiting means to cam said roller element in said first direction whereby to permit said leaf spring to move said one of said contact members out of engagement with the other.

5. An electrical switch comprising a pair of electric contact members, at least one of said contact members including yieldable means urging said one contact member out of engagement with the other, a plunger having a camming projection thereon, a roller element in rolling engagement between said plunger and said one of said contact members, and guide means other than said plunger for guiding said roller element, said guide means permitting limited movement of said roller element in the direction of movement of said plunger and permitting movement of said roller element to engage and disengage said contact elements, said projection being effective upon movement of said plunger in a first direction and upon limiting of said roller element by said guide means to cam said roller element against said one contact member whereby to cause engagement of said contact members, and said projection being effective upon movement of said plunger in the opposite direction and upon limiting of said roller element by said guide means to carn said roller element in said first direction whereby to enable said yieldable means to move said one contact member out of engagement with the other.

6. An electrical switch comprising a pair of electric contact members, at least one of said contact members including a leaf spring urging said one Contact member out of engagement with the other, a plunger having a camming projection thereon, and a ball in rolling engagement between said plunger and said leaf spring, said projection being effective upon movement of said plunger in a first direction to cam said ball against said leaf spring whereby to cause engagement of said contact members, and means other than said plunger for limiting movement of said ball in the direction of movement of said plunger, said projection being effective upon movement of said plunger in the opposite direction to cam said ball in said first direction and along said plunger whereby to enable said leaf spring to disengage said contact members.

7. An electrical switch comprising a casing, a pair of electric contacts in sai-d casing, a leaf spring supporting one of said contacts and yieldably urging said one contact out of engagement with the other, said casing having a guide slot in one Wall thereof, a plunger having a camming projection thereon, and a roller element in said guide slot and in rolling engagement between said plunger and said leaf spring, said slot limiting movement `of said roller member in the direction of movement of said lplunger and permitting movement of Said rol-ler member at right angles to the direction of movement of said plunger whereby to engage and disengage said contacts, said projection being effective upon movement of said plunger in a first direction to cam said roller element toward said one contact whereby to cause engagement of said contacts, and said projection being effective upon movement of said plunger in the opposite direction to cam said roller element in said first direction whereby to enable said spring to disengage said contacts.

8. An electrical switch comprising a casing, a pair of electric contacts in said casing, a leaf spring supporting one of said contacts at one end and anchored in said casing adjacent the opposite end, said spring yieldably urging said one contact out of engagement with the other; said casing having a guide s'lot in one wall thereof, a depressible key having a camming projection thereon, means for guiding said key past said casing, spring means for returning said key from depressed condition, and a roller element in sai-d slot and in rolling engagement between said leaf spring and said key, said projection being effective upon depression of said key in one direction to cam said roller element against said leaf spring whereby to cause engagement of said contacts, and said projection being effective upon return of said key in the opposite direction to cam said roller element in said one direction whereby to enable said leaf spring t-o disengage said one contact from the other.

9. An electrical switch comprising a two-part casing including a yfirst casing part and a second casing part; said casing parts having interengaging surfaces for locating said casing parts relative to each other, a pair of contacts in said casing, means supporting a rst one of said contacts, an elongate leaf spring attached at one end thereto to a second one of said contacts, said casing parts having cooperating surfaces for receiving the opposite end of said leaf spring whereby to normally locate said one end of said second contact out of engagement with said first conta-ct, said casing having a guide slot in one wall thereof, a depressible key having a camming projection thereon, means for guiding said key past said casing, spring means for returning said key from depressed condi-tion, and a roller element in said slot and in rolling engagement between said leaf spring and sai-d key, said projection 'being eective upon depression of said key in one direction and limiting of said r-ol'ler element against one end of said guide slot to cam said roller element lagainst said leaf spring whereby to cause engagement of said contacts, and said projection being effective upon return of said key from depressed condition and limiting of said roller element against the opposite end of said guide slot to cam said roller element in said one direction whereby to enable said leaf spring to disengage said one contact from the other.

10. An electrical switch comprising a two-part casing including a first casing part and a second casing part; said casing parts having interengaging surfaces for 1ocating said casing parts relative to each other, means for securing said casing parts together, a pair of elongate spring members in said casing, said spring members each having an electric contact at one end thereof, said casing parts having cooperating surfaces for receiving the opposite ends of said spring members therebetween whereby to normally locate said spring members and said contacts in spaced relation, said casing having a guide slot in one Wall thereof, a depressible key having a camming projection thereon, means for guiding said key past Said casing, spring means for returning said key from depressed condition, and a roller element in Said slot and in rolling engagement between one of said spring members and said key, said projection being effective upon depression of said key in Vone direction and limiting of said roller element against one end of said guide slot to cam said roller element against said one of said spring members whereby to cause engagement of said contacts, and said projecti-on being effective upon return of said key in the opposite direction `and limiting of said roller element against the :opposite end of said guide slot to cam said roller element in said one direction whereby to enable said spring members to disengage said contacts.

References Cited by the Examiner UNITED STATES PATENTS 2,471,568 5/ 1949 Harrison. 3,001,042 9/ 1961 Cherry 200-67 3,098,905 7/1963 Anderson 200-166 X 3,138,780 6/1'964 Jacobsen 20G- 153 X FOREIGN PATENTS 550,172 5/ 1932 Germany.

BERNARD A. GILHEANY, Primary Examiner. 

1. AN ELECTRICAL SWITCH COMPRISING A PAIR OF ELECTRIC CONTACT MEMBERS, AT LEAST ONE OF SAID MEMBERS INCLUDING A SPRING NORMALLY MAINTAINING SAID CONTACT MEMBERS OUT OF ENGAGEMENT WITH THE OTHER, A PLUNGER HAVING A CAMMING PROJECTION THEREON, AND A ROLLER ELEMENT IN ROLLING ENGAGEMENT BETWEEN SAID PLUNGER AND SAID ONE OF SAID CONTACT MEMBERS, SAID PROJECTION BEING EFFECTIVE UPON MOVEMENT OF SAID PLUNGER IN ONE DIRECTION TO CAM SAID ROLLER ELEMENT AT RIGHT ANGLES TO SAID ONE DIRECTION TOWARD SAID ONE CONTACT MEMBER WHEREBY TO CAUSE ENGAGEMENT OF SAID CONTACT MEMBERS, AND MEANS OTHER THAN SAID PLUNGER FOR PERMITTING LIMITED MOVEMENT OF SAID ROLLER ELEMENT IN THE DIRECTION OF MOVEMENT OF SAID PLUNGER, SAID PROJECTION BEING EFFECTIVE UPON MOVEMENT OF SAID PLUNER IN THE DIRECTION OPPOSITE SAID ONE DIRECTION TO CAM SAID ROLLER ELEMENT IN SAID ONE DIRECTION WHEREBY TO ENABLE SAID SPRING TO DISENGAGE SAID CONTACT MEMBERS. 